1. Field of the Invention
This invention relates to the field of sealant compositions and more specifically to sealant compositions comprising inverse emulsion polymers as well as methods for using such compositions to service a wellbore.
2. Background of the Invention
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (e.g., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. Subsequent secondary cementing operations may also be performed. One example of a secondary cementing operation is squeeze cementing whereby a cement slurry is employed to plug and seal off undesirable flow passages in the cement sheath and/or the casing. While a cement slurry is one type of sealant composition used in primary and secondary cementing operations, other non-cement containing sealant compositions may also be employed.
For instance, a process known as gunk-squeeze involves placing a gunk plug in a lost circulation zone to reduce fluid loss. Gunk-squeeze involves mixing a clay such as bentonite with a diesel and placing the mixture in the wellbore where the clay contacts water to form a sealant composition. Drawbacks include downhole delivery problems such as mixing the water with the clay in the wellbore. Further drawbacks include the gunk-squeeze process typically being insufficient for vugular losses because the composition has a slow reacting chemistry. Other processes include using particles to seal lost circulation zones. Drawbacks to such processes include operating costs (e.g., increased pumping costs). Further drawbacks include insufficient plugging of large lost circulation zones.
Consequently, there is a need for an improved sealant composition. Further needs include a sealant composition that is sufficient for plugging lost circulation zones and that is easily delivered downhole.